Expression and characterization of a putative high affinity human soluble leptin receptor

Area of Science:

• Molecular Endocrinology
• Obesity Research

Background:

• Leptin regulates body weight by influencing food intake and energy expenditure.
• Leptin receptors (ObR) are crucial for leptin signaling, with genetic mutations causing obesity.
• Differential splicing of ObR mRNA has been identified.

Purpose of the Study:

• To characterize the binding properties of a soluble leptin receptor (sObR) expressed in vitro.
• To investigate the potential of sObR as a tool for studying leptin's function.

Main Methods:

• Expression of full-length and extracellular domains of human leptin receptor in COS7 cells.
• Radioligand binding assays using 125I-leptin.
• Cross-linking studies and HPLC gel filtration to analyze receptor complexes.
• Western blot and Coomassie staining for protein characterization.

Main Results:

• High-affinity binding of 125I-leptin to membrane-bound full-length ObR (Ki ≈ 200 pM).
• Identification of a soluble leptin receptor in conditioned medium with high-affinity binding for human and mouse leptin.
• Characterization of 125I-leptin/sObR complexes, including a homodimer of approximately 300-340 kDa.
• Demonstration that sObR antagonizes leptin binding to membrane receptors.

Conclusions:

• A soluble form of the leptin receptor can be produced and secreted.
• The soluble leptin receptor exhibits high-affinity leptin binding and can form dimers.
• Soluble leptin receptor acts as an antagonist, suggesting its utility in elucidating endogenous leptin roles.